Joannah Hinz - Academia.edu (original) (raw)

Papers by Joannah Hinz

Abstract. New Spitzer images of M101 from 3.5 to 160 µm are presented. Preliminary analysis focus... more Abstract. New Spitzer images of M101 from 3.5 to 160 µm are presented. Preliminary analysis focusing on the dependence of the infrared spectral energy distribution of HII regions as a function of metallicity finds that the mid-infrared PAH features become weak or absent between metallicities of 8.5 and 8.1. There is also a trend towards hotter dust temperature as metallicity decreases. M101 is a large (> 30 diameter), face-on spiral galaxy at a distance of 6.7 kpc Sufficient infrared spatial resolution and sensitivity to study bright and faint HII regions in M101 is now possible with the launch of the Spitzer Space Telescope (Spitzer, Werner et al. 2004). Our program utilizes the imaging and spectroscopic capabilities of Spitzer to study the metallicity dependence of the spectral energy distributions (SEDs) in M101 HII regions. Spitzer imaging of M101 has been obtained with the Infrared Array Camera (IRAC, Fazio et al. 2004) at 3.6, 4.5, 5.8, 8.0 µm and with the Multiband Imaging...

The nearby late M star Gliese 569B was recently found by adaptive optics imaging to be a double w... more The nearby late M star Gliese 569B was recently found by adaptive optics imaging to be a double with separation ∼ 1 AU. To explore the orbital motion and masses, we have undertaken a high resolution (∼ 0. 05) astrometric study. Images were obtained over 1.5 years with bispectrum speckle interferometry at the 6.5m MMT and 6m SAO telescopes. Our data show motion corresponding to more than half the orbital period, and constrain the total mass to be > 0.115 M⊙, with a most probable value of 0.145 M⊙. Higher masses cannot be excluded without more extended observations, but from statistical analysis we find an 80% probability that the total mass is less than 0.21 M⊙. An infrared spectrum of the blended B double obtained with the MMT has been modeled as a blend of two different spectral types, chosen to be consistent with the measured J and K band brightness difference of a factor ∼ 2. The blended fit is not nearly as good as that to a pure M8.5+ template. Therefore we hypothesize that ...

The Astronomical Journal, 2002

A common proper motion survey of M dwarf stars within 8 pc of the Sun reveals no new stellar or b... more A common proper motion survey of M dwarf stars within 8 pc of the Sun reveals no new stellar or brown dwarf companions at wide separations (∼ 100-1400 AU). This survey tests whether the brown dwarf "desert" extends to large separations around M dwarf stars and further explores the census of the solar neighborhood. The sample includes 66 stars north of −30 • and within 8 pc of the Sun. Existing first epoch images are compared to new J-band images of the same fields an average of 7 years later to reveal proper motion companions within a ∼ 4 arcminute radius of the primary star. No new companions are detected to a J-band limiting magnitude of ∼ 16.5, corresponding to a companion mass of ∼ 40 Jupiter masses for an assumed age of 5 Gyr at the mean distance of the objects in the survey, 5.8 pc.

Being the biggest asteroid with a reasonably intact basaltic crust, 4 Vesta is a pivotal object t... more Being the biggest asteroid with a reasonably intact basaltic crust, 4 Vesta is a pivotal object to the understanding of the early history of the Solar System. Attempts to map the mineralogical variations on its surface include earth-based spectroscopy on the 0.8-2.5mu m range as well as disk-resolved observations with the HST between 0.4-1.0mu m and JHK imaging with adaptive optics with the Keck Telescope. However,the observations of 4 Vesta during the 1997 opposition with the HST/NICMOS are the first to combine spatial resolution and full rotational coverage with a set of filters that covers the most mineralogically relevant spectral features of HED assemblages. The NICMOS data were all acquired within a 5-day interval, with Vesta's sub-earth latitude varying from -2.8 to -3.5o. Narrow-band filters centered on 0.9536, 1.1298, 1.606, 1.8986 and 2.1641 mu m and medium-band filters on 1.4556 and 2.2181 mu m were used. For each filter, full rotational coverage was obtained, with i...

We present ultraviolet, optical, near-infrared, Spitzer mid-infrared, and radio images of 14 radi... more We present ultraviolet, optical, near-infrared, Spitzer mid-infrared, and radio images of 14 radio-selected objects in M 33. These objects are thought to represent the youngest phase of star cluster formation. We have detected the majority of cluster candidates in M 33 at all wavelengths. From the near-IR images, we derived ages 2-10 Myr, K_S-band extinctions (A_K_S) of 0-1 mag, and stellar masses of 10^3-10^4 M_solar. We have generated spectral energy distributions (SEDs) of each cluster from 0.1 micron to 160 microns. From these SEDs, we have modeled the dust emission around these star clusters to determine the dust masses (1-10^3 M_solar) and temperatures (40-90 K) of the clusters' local interstellar medium. Extinctions derived from the JHK_S, Halpha, and UV images are similar to within a factor of 2 or 3. These results suggest that eleven of the fourteen radio-selected objects are optically-visible young star clusters with a surrounding H II region, that two are background o...

We present observations of the spiral galaxy M33 with Spitzer at 24, 70, and 160 m. The excellent... more We present observations of the spiral galaxy M33 with Spitzer at 24, 70, and 160 m. The excellent resolution and mapping capabilities of Spitzer combined with the proximity of M33 result in observations that enable a detailed study of the distribution of star formation (SF) and dust in the galaxy. We compare the morphology of M33 at far-infrared wavelengths with other standard SF indicators such as H and radio continuum using a Fourier filtering technique to separate the diffuse emission components from compact sources. We find that the infrared emission at 24 and 70 m follows closely the structure of the ionized gas, indicating that it is heated largely by hot, ionizing stars. At 160 m a diffuse cold dust component matches only approximately the structure of the old red stellar population or the distribution of blue light. It is, however, very similar to the structure of the diffuse nonthermal radio emission.

Monthly Notices of the Royal Astronomical Society, 2014

We present a catalogue and images of visually detected features, such as asymmetries, extensions,... more We present a catalogue and images of visually detected features, such as asymmetries, extensions, warps, shells, tidal tails, polar rings, and obvious signs of mergers or interactions, in the faint outer regions (at and outside of R 25) of nearby galaxies. This catalogue can be used in future quantitative studies that examine galaxy evolution due to internal and external factors. We are able to reliably detect outer region features down to a brightness level of 0.03 MJy/sr per pixel at 3.6 µm in the Spitzer Survey of Stellar Structure in Galaxies (S 4 G). We also tabulate companion galaxies. We find asymmetries in the outer isophotes in 22±1 per cent of the sample. The asymmetry fraction does not correlate with galaxy classification as an interacting galaxy or merger remnant, or with the presence of companions. We also compare the detected features to similar features in galaxies taken from cosmological zoom re-simulations. The simulated images have a higher fraction (33 per cent) of outer disc asymmetries, which may be due to selection effects and an uncertain star formation threshold in the models. The asymmetries may have either an internal (e.g., lopsidedness due to dark halo asymmetry) or external origin.

The Astrophysical Journal, 2021

Wu & Peek predict SDSS-quality spectra based on Pan-STARRS broadband grizy images using machine l... more Wu & Peek predict SDSS-quality spectra based on Pan-STARRS broadband grizy images using machine learning (ML). In this article, we test their prediction for a unique object, UGC 2885 (“Rubin’s galaxy”), the largest and most massive, isolated disk galaxy in the local universe (D < 100 Mpc). After obtaining the ML predicted spectrum, we compare it to all existing spectroscopic information that is comparable to an SDSS spectrum of the central region: two archival spectra, one extracted from the VIRUS-P observations of this galaxy, and a new, targeted MMT/Binospec observation. Agreement is qualitatively good, though the ML prediction prefers line ratios slightly more toward those of an active galactic nucleus (AGN), compared to archival and VIRUS-P observed values. The MMT/Binospec nuclear spectrum unequivocally shows strong emission lines except Hβ, the ratios of which are consistent with AGN activity. The ML approach to galaxy spectra may be a viable way to identify AGN supplementi...

Spitzer Proposal, Dec 1, 2008

ABSTRACT The Spitzer Survey of Stellar Structure in Galaxies ( 4 G ) is an Exploration Science Le... more ABSTRACT The Spitzer Survey of Stellar Structure in Galaxies ( 4 G ) is an Exploration Science Legacy Program approved for the Spitzer post-cryogenic mission. It is a volume-, magnitude-, and size-limited ( d &lt; 40 Mpc , | b | &gt; 30 ° , mBcorr &lt; 15.5 , and D25 &gt; 1&amp;apos;) survey of 2331 galaxies using the Infrared Array Camera (IRAC) at 3.6 and 4.5 μm. Each galaxy is observed for 240 s and mapped to ≥ 1.5 × D25 . The final mosaicked images have a typical 1σ rms noise level of 0.0072 and 0.0093 MJy sr-1 at 3.6 and 4.5 μm, respectively. Our azimuthally averaged surface brightness profile typically traces isophotes at μ3.6 μm ( AB ) ( 1 σ ) ˜ 27 mag arcsec-2 , equivalent to a stellar mass surface density of ˜ 1 Mȯ pc-2. S4 G thus provides an unprecedented data set for the study of the distribution of mass and stellar structures in the local universe. This large, unbiased, and extremely deep sample of all Hubble types from dwarfs to spirals to ellipticals will allow for detailed structural studies, not only as a function of stellar mass, but also as a function of the local environment. The data from this survey will serve as a vital testbed for cosmological simulations predicting the stellar mass properties of present-day galaxies. This article introduces the survey and describes the sample selection, the significance of the 3.6 and 4.5 μm bands for this study, and the data collection and survey strategies. We describe the S4 G data analysis pipeline and present measurements for a first set of galaxies, observed in both the cryogenic and warm mission phases of Spitzer. For every galaxy we tabulate the galaxy diameter, position angle, axial ratio, inclination at μ3.6 μm ( AB ) = 25.5 , and 26.5 mag arcsec-2 (equivalent to ≈ μB ( AB ) = 27.2 and 28.2 mag arcsec-2 , respectively). These measurements will form the initial S4 G catalog of galaxy properties. We also measure the total magnitude and the azimuthally averaged radial profiles of ellipticity, position angle, surface brightness, and color. Finally, using the galaxy-fitting code GALFIT, we deconstruct each galaxy into its main constituent stellar components: the bulge/spheroid, disk, bar, and nuclear point source, where necessary. Together, these data products will provide a comprehensive and definitive catalog of stellar structures, mass, and properties of galaxies in the nearby universe and will enable a variety of scientific investigations, some of which are highlighted in this introductory S4 G survey paper.

We present 3.6-8 micron observations of the Andromeda galaxy, M31, obtained with the Infrared Arr... more We present 3.6-8 micron observations of the Andromeda galaxy, M31, obtained with the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope. The image mosaics cover areas of approximately 3.7 x 1.6 deg and include the M31 satellite galaxies M32 and NGC 205. ...

Publ Astron Soc Pac, 2001

Bulletin of the American Astronomical Society, Nov 29, 2004

New far-infrared images at 24, 70, and 160 microns from the Multiband Imaging Photometer for Spit... more New far-infrared images at 24, 70, and 160 microns from the Multiband Imaging Photometer for Spitzer (MIPS) are presented covering the full optical disk of M31 (1x3 degrees) including the satellite galaxies M32 and NGC 205. These new infrared images reveal intricate details of the nuclear region and multiple star forming arms/rings in M31. When combined with new and existing

Spitzer Proposal, May 1, 2006

ABSTRACT NGC 1097 has an extensive, unique network of jet-like extended structures that stretch o... more ABSTRACT NGC 1097 has an extensive, unique network of jet-like extended structures that stretch out for dozens of kiloparsecs. Their origin has remained a mystery for decades. The evidence for their association with the AGN is weak, and the lack of HI emission in the vicinity makes it unlikely that they are the product of tidal interactions or streams off the main disk of the galaxy. Recent modeling has shown that the structures may be the remnants of a dwarf galaxy, though the type of dwarf remains unclear, and such interactions are complicated by the fact that the main spiral has a large bar. We propose Spitzer observations of these features to determine the streams&#39; true extent, to age-date individual structures by focusing on the old stellar population, estimate their masses, and calculate their metallicities. We will use Spitzer&#39;s sensitivity and the degeneracy-breaking IRAC colors to unravel the history of this unusual object. This proposal is part of broader studies by members of this team on galaxy outskirts and interactions, including mergers, streams, shells, asymmetries and lopsidedness, all of which contribute to our understanding of galaxy evolution in the nearby Universe.

We present a catalogue and images of visually detected features, such as asymmetries, extensions,... more We present a catalogue and images of visually detected features, such as asymmetries, extensions, warps, shells, tidal tails, polar rings, and obvious signs of mergers or interactions, in the faint outer regions (at and outside of R 25) of nearby galaxies. This catalogue can be used in future quantitative studies that examine galaxy evolution due to internal and external factors. We are able to reliably detect outer region features down to a brightness level of 0.03 MJy/sr per pixel at 3.6 µm in the Spitzer Survey of Stellar Structure in Galaxies (S 4 G). We also tabulate companion galaxies. We find asymmetries in the outer isophotes in 22±1 per cent of the sample. The asymmetry fraction does not correlate with galaxy classification as an interacting galaxy or merger remnant, or with the presence of companions. We also compare the detected features to similar features in galaxies taken from cosmological zoom re-simulations. The simulated images have a higher fraction (33 per cent) of outer disc asymmetries, which may be due to selection effects and an uncertain star formation threshold in the models. The asymmetries may have either an internal (e.g., lopsidedness due to dark halo asymmetry) or external origin.

Thesis the University of Arizona Source Dai B 64 05 P 2227 Nov 2003 99 Pages, Nov 1, 2003

The origin of the tight radio--IR correlation in galaxies has not been fully understood. One reas... more The origin of the tight radio--IR correlation in galaxies has not been fully understood. One reason is the uncertainty about which heating sources (stars or diffuse interstellar radiation field)provide the energy that is absorbed by dust and re-radiated in IR. Another problem is caused by comparing the IR emission with the thermal and nonthermal components of the radio continuum emission separated by simplistically assuming a constant nonthermal spectral index. We use the data at the SpitzerSpitzerSpitzer MIPS wavelengths of 24, 70, and 160 mu\mumum, as well as recent radio continuum map at 3.6 cm observed with the 100--m Effelsberg telescope. Using the wavelet transformation, we separate diffuse emission components from compact sources and study the radio-IR correlation at various scales. We also investigate the IR correlations with the thermal and nonthermal radio emissions separated by our developed method. A H$\alpha$ map serves as a tracer of star forming regions.

AIP Conference Proceedings, 2005

Spitzer provides substantial advances for studies of external galaxies: 1.) it has the very high ... more Spitzer provides substantial advances for studies of external galaxies: 1.) it has the very high sensitivity toward extended, low-surface-brightness sources made possible by a cryogenic telescope in space; 2.) the use of large format arrays and projected pixel scales that sample the telescope image well provide substantial improvements in angular resolution compared with previous space infrared telescopes; and 3.) its spectrograph has wavelength resolution well-suited to extragalactic studies, as well as high performance arrays that provide a major advance in sensitivity. We show how these capabilities are already leading to new possibilities in studying the structure of nearby galaxies. Combined with recent breakthroughs in high quality imaging at other wavelengths, we can anticipate a substantial improvement in our understanding of how different components of a galaxy relate to each other and how their interactions influence galaxy evolution. In addition, Spitzer is advancing our understanding of the behavior of the polyaromatic hydrocarbon (PAH) emission features, as a function of environment and metallicity. New features are also being discovered due to the high-sensitivity mapping capabilities of the spectrograph. An additional direction for research with Spitzer arises from its deep survey capabilities and the possibility of testing how the spectral energy distributions of galaxies evolve at large look-back times.

Abstract. New Spitzer images of M101 from 3.5 to 160 µm are presented. Preliminary analysis focus... more Abstract. New Spitzer images of M101 from 3.5 to 160 µm are presented. Preliminary analysis focusing on the dependence of the infrared spectral energy distribution of HII regions as a function of metallicity finds that the mid-infrared PAH features become weak or absent between metallicities of 8.5 and 8.1. There is also a trend towards hotter dust temperature as metallicity decreases. M101 is a large (> 30 diameter), face-on spiral galaxy at a distance of 6.7 kpc Sufficient infrared spatial resolution and sensitivity to study bright and faint HII regions in M101 is now possible with the launch of the Spitzer Space Telescope (Spitzer, Werner et al. 2004). Our program utilizes the imaging and spectroscopic capabilities of Spitzer to study the metallicity dependence of the spectral energy distributions (SEDs) in M101 HII regions. Spitzer imaging of M101 has been obtained with the Infrared Array Camera (IRAC, Fazio et al. 2004) at 3.6, 4.5, 5.8, 8.0 µm and with the Multiband Imaging...

The nearby late M star Gliese 569B was recently found by adaptive optics imaging to be a double w... more The nearby late M star Gliese 569B was recently found by adaptive optics imaging to be a double with separation ∼ 1 AU. To explore the orbital motion and masses, we have undertaken a high resolution (∼ 0. 05) astrometric study. Images were obtained over 1.5 years with bispectrum speckle interferometry at the 6.5m MMT and 6m SAO telescopes. Our data show motion corresponding to more than half the orbital period, and constrain the total mass to be > 0.115 M⊙, with a most probable value of 0.145 M⊙. Higher masses cannot be excluded without more extended observations, but from statistical analysis we find an 80% probability that the total mass is less than 0.21 M⊙. An infrared spectrum of the blended B double obtained with the MMT has been modeled as a blend of two different spectral types, chosen to be consistent with the measured J and K band brightness difference of a factor ∼ 2. The blended fit is not nearly as good as that to a pure M8.5+ template. Therefore we hypothesize that ...

The Astronomical Journal, 2002

A common proper motion survey of M dwarf stars within 8 pc of the Sun reveals no new stellar or b... more A common proper motion survey of M dwarf stars within 8 pc of the Sun reveals no new stellar or brown dwarf companions at wide separations (∼ 100-1400 AU). This survey tests whether the brown dwarf "desert" extends to large separations around M dwarf stars and further explores the census of the solar neighborhood. The sample includes 66 stars north of −30 • and within 8 pc of the Sun. Existing first epoch images are compared to new J-band images of the same fields an average of 7 years later to reveal proper motion companions within a ∼ 4 arcminute radius of the primary star. No new companions are detected to a J-band limiting magnitude of ∼ 16.5, corresponding to a companion mass of ∼ 40 Jupiter masses for an assumed age of 5 Gyr at the mean distance of the objects in the survey, 5.8 pc.

Being the biggest asteroid with a reasonably intact basaltic crust, 4 Vesta is a pivotal object t... more Being the biggest asteroid with a reasonably intact basaltic crust, 4 Vesta is a pivotal object to the understanding of the early history of the Solar System. Attempts to map the mineralogical variations on its surface include earth-based spectroscopy on the 0.8-2.5mu m range as well as disk-resolved observations with the HST between 0.4-1.0mu m and JHK imaging with adaptive optics with the Keck Telescope. However,the observations of 4 Vesta during the 1997 opposition with the HST/NICMOS are the first to combine spatial resolution and full rotational coverage with a set of filters that covers the most mineralogically relevant spectral features of HED assemblages. The NICMOS data were all acquired within a 5-day interval, with Vesta's sub-earth latitude varying from -2.8 to -3.5o. Narrow-band filters centered on 0.9536, 1.1298, 1.606, 1.8986 and 2.1641 mu m and medium-band filters on 1.4556 and 2.2181 mu m were used. For each filter, full rotational coverage was obtained, with i...

We present ultraviolet, optical, near-infrared, Spitzer mid-infrared, and radio images of 14 radi... more We present ultraviolet, optical, near-infrared, Spitzer mid-infrared, and radio images of 14 radio-selected objects in M 33. These objects are thought to represent the youngest phase of star cluster formation. We have detected the majority of cluster candidates in M 33 at all wavelengths. From the near-IR images, we derived ages 2-10 Myr, K_S-band extinctions (A_K_S) of 0-1 mag, and stellar masses of 10^3-10^4 M_solar. We have generated spectral energy distributions (SEDs) of each cluster from 0.1 micron to 160 microns. From these SEDs, we have modeled the dust emission around these star clusters to determine the dust masses (1-10^3 M_solar) and temperatures (40-90 K) of the clusters' local interstellar medium. Extinctions derived from the JHK_S, Halpha, and UV images are similar to within a factor of 2 or 3. These results suggest that eleven of the fourteen radio-selected objects are optically-visible young star clusters with a surrounding H II region, that two are background o...

We present observations of the spiral galaxy M33 with Spitzer at 24, 70, and 160 m. The excellent... more We present observations of the spiral galaxy M33 with Spitzer at 24, 70, and 160 m. The excellent resolution and mapping capabilities of Spitzer combined with the proximity of M33 result in observations that enable a detailed study of the distribution of star formation (SF) and dust in the galaxy. We compare the morphology of M33 at far-infrared wavelengths with other standard SF indicators such as H and radio continuum using a Fourier filtering technique to separate the diffuse emission components from compact sources. We find that the infrared emission at 24 and 70 m follows closely the structure of the ionized gas, indicating that it is heated largely by hot, ionizing stars. At 160 m a diffuse cold dust component matches only approximately the structure of the old red stellar population or the distribution of blue light. It is, however, very similar to the structure of the diffuse nonthermal radio emission.

Monthly Notices of the Royal Astronomical Society, 2014

We present a catalogue and images of visually detected features, such as asymmetries, extensions,... more We present a catalogue and images of visually detected features, such as asymmetries, extensions, warps, shells, tidal tails, polar rings, and obvious signs of mergers or interactions, in the faint outer regions (at and outside of R 25) of nearby galaxies. This catalogue can be used in future quantitative studies that examine galaxy evolution due to internal and external factors. We are able to reliably detect outer region features down to a brightness level of 0.03 MJy/sr per pixel at 3.6 µm in the Spitzer Survey of Stellar Structure in Galaxies (S 4 G). We also tabulate companion galaxies. We find asymmetries in the outer isophotes in 22±1 per cent of the sample. The asymmetry fraction does not correlate with galaxy classification as an interacting galaxy or merger remnant, or with the presence of companions. We also compare the detected features to similar features in galaxies taken from cosmological zoom re-simulations. The simulated images have a higher fraction (33 per cent) of outer disc asymmetries, which may be due to selection effects and an uncertain star formation threshold in the models. The asymmetries may have either an internal (e.g., lopsidedness due to dark halo asymmetry) or external origin.

The Astrophysical Journal, 2021

Wu & Peek predict SDSS-quality spectra based on Pan-STARRS broadband grizy images using machine l... more Wu & Peek predict SDSS-quality spectra based on Pan-STARRS broadband grizy images using machine learning (ML). In this article, we test their prediction for a unique object, UGC 2885 (“Rubin’s galaxy”), the largest and most massive, isolated disk galaxy in the local universe (D < 100 Mpc). After obtaining the ML predicted spectrum, we compare it to all existing spectroscopic information that is comparable to an SDSS spectrum of the central region: two archival spectra, one extracted from the VIRUS-P observations of this galaxy, and a new, targeted MMT/Binospec observation. Agreement is qualitatively good, though the ML prediction prefers line ratios slightly more toward those of an active galactic nucleus (AGN), compared to archival and VIRUS-P observed values. The MMT/Binospec nuclear spectrum unequivocally shows strong emission lines except Hβ, the ratios of which are consistent with AGN activity. The ML approach to galaxy spectra may be a viable way to identify AGN supplementi...

Spitzer Proposal, Dec 1, 2008

ABSTRACT The Spitzer Survey of Stellar Structure in Galaxies ( 4 G ) is an Exploration Science Le... more ABSTRACT The Spitzer Survey of Stellar Structure in Galaxies ( 4 G ) is an Exploration Science Legacy Program approved for the Spitzer post-cryogenic mission. It is a volume-, magnitude-, and size-limited ( d &lt; 40 Mpc , | b | &gt; 30 ° , mBcorr &lt; 15.5 , and D25 &gt; 1&amp;apos;) survey of 2331 galaxies using the Infrared Array Camera (IRAC) at 3.6 and 4.5 μm. Each galaxy is observed for 240 s and mapped to ≥ 1.5 × D25 . The final mosaicked images have a typical 1σ rms noise level of 0.0072 and 0.0093 MJy sr-1 at 3.6 and 4.5 μm, respectively. Our azimuthally averaged surface brightness profile typically traces isophotes at μ3.6 μm ( AB ) ( 1 σ ) ˜ 27 mag arcsec-2 , equivalent to a stellar mass surface density of ˜ 1 Mȯ pc-2. S4 G thus provides an unprecedented data set for the study of the distribution of mass and stellar structures in the local universe. This large, unbiased, and extremely deep sample of all Hubble types from dwarfs to spirals to ellipticals will allow for detailed structural studies, not only as a function of stellar mass, but also as a function of the local environment. The data from this survey will serve as a vital testbed for cosmological simulations predicting the stellar mass properties of present-day galaxies. This article introduces the survey and describes the sample selection, the significance of the 3.6 and 4.5 μm bands for this study, and the data collection and survey strategies. We describe the S4 G data analysis pipeline and present measurements for a first set of galaxies, observed in both the cryogenic and warm mission phases of Spitzer. For every galaxy we tabulate the galaxy diameter, position angle, axial ratio, inclination at μ3.6 μm ( AB ) = 25.5 , and 26.5 mag arcsec-2 (equivalent to ≈ μB ( AB ) = 27.2 and 28.2 mag arcsec-2 , respectively). These measurements will form the initial S4 G catalog of galaxy properties. We also measure the total magnitude and the azimuthally averaged radial profiles of ellipticity, position angle, surface brightness, and color. Finally, using the galaxy-fitting code GALFIT, we deconstruct each galaxy into its main constituent stellar components: the bulge/spheroid, disk, bar, and nuclear point source, where necessary. Together, these data products will provide a comprehensive and definitive catalog of stellar structures, mass, and properties of galaxies in the nearby universe and will enable a variety of scientific investigations, some of which are highlighted in this introductory S4 G survey paper.

We present 3.6-8 micron observations of the Andromeda galaxy, M31, obtained with the Infrared Arr... more We present 3.6-8 micron observations of the Andromeda galaxy, M31, obtained with the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope. The image mosaics cover areas of approximately 3.7 x 1.6 deg and include the M31 satellite galaxies M32 and NGC 205. ...

Publ Astron Soc Pac, 2001

Bulletin of the American Astronomical Society, Nov 29, 2004

New far-infrared images at 24, 70, and 160 microns from the Multiband Imaging Photometer for Spit... more New far-infrared images at 24, 70, and 160 microns from the Multiband Imaging Photometer for Spitzer (MIPS) are presented covering the full optical disk of M31 (1x3 degrees) including the satellite galaxies M32 and NGC 205. These new infrared images reveal intricate details of the nuclear region and multiple star forming arms/rings in M31. When combined with new and existing

Spitzer Proposal, May 1, 2006

ABSTRACT NGC 1097 has an extensive, unique network of jet-like extended structures that stretch o... more ABSTRACT NGC 1097 has an extensive, unique network of jet-like extended structures that stretch out for dozens of kiloparsecs. Their origin has remained a mystery for decades. The evidence for their association with the AGN is weak, and the lack of HI emission in the vicinity makes it unlikely that they are the product of tidal interactions or streams off the main disk of the galaxy. Recent modeling has shown that the structures may be the remnants of a dwarf galaxy, though the type of dwarf remains unclear, and such interactions are complicated by the fact that the main spiral has a large bar. We propose Spitzer observations of these features to determine the streams&#39; true extent, to age-date individual structures by focusing on the old stellar population, estimate their masses, and calculate their metallicities. We will use Spitzer&#39;s sensitivity and the degeneracy-breaking IRAC colors to unravel the history of this unusual object. This proposal is part of broader studies by members of this team on galaxy outskirts and interactions, including mergers, streams, shells, asymmetries and lopsidedness, all of which contribute to our understanding of galaxy evolution in the nearby Universe.

We present a catalogue and images of visually detected features, such as asymmetries, extensions,... more We present a catalogue and images of visually detected features, such as asymmetries, extensions, warps, shells, tidal tails, polar rings, and obvious signs of mergers or interactions, in the faint outer regions (at and outside of R 25) of nearby galaxies. This catalogue can be used in future quantitative studies that examine galaxy evolution due to internal and external factors. We are able to reliably detect outer region features down to a brightness level of 0.03 MJy/sr per pixel at 3.6 µm in the Spitzer Survey of Stellar Structure in Galaxies (S 4 G). We also tabulate companion galaxies. We find asymmetries in the outer isophotes in 22±1 per cent of the sample. The asymmetry fraction does not correlate with galaxy classification as an interacting galaxy or merger remnant, or with the presence of companions. We also compare the detected features to similar features in galaxies taken from cosmological zoom re-simulations. The simulated images have a higher fraction (33 per cent) of outer disc asymmetries, which may be due to selection effects and an uncertain star formation threshold in the models. The asymmetries may have either an internal (e.g., lopsidedness due to dark halo asymmetry) or external origin.

Thesis the University of Arizona Source Dai B 64 05 P 2227 Nov 2003 99 Pages, Nov 1, 2003

The origin of the tight radio--IR correlation in galaxies has not been fully understood. One reas... more The origin of the tight radio--IR correlation in galaxies has not been fully understood. One reason is the uncertainty about which heating sources (stars or diffuse interstellar radiation field)provide the energy that is absorbed by dust and re-radiated in IR. Another problem is caused by comparing the IR emission with the thermal and nonthermal components of the radio continuum emission separated by simplistically assuming a constant nonthermal spectral index. We use the data at the SpitzerSpitzerSpitzer MIPS wavelengths of 24, 70, and 160 mu\mumum, as well as recent radio continuum map at 3.6 cm observed with the 100--m Effelsberg telescope. Using the wavelet transformation, we separate diffuse emission components from compact sources and study the radio-IR correlation at various scales. We also investigate the IR correlations with the thermal and nonthermal radio emissions separated by our developed method. A H$\alpha$ map serves as a tracer of star forming regions.

AIP Conference Proceedings, 2005

Spitzer provides substantial advances for studies of external galaxies: 1.) it has the very high ... more Spitzer provides substantial advances for studies of external galaxies: 1.) it has the very high sensitivity toward extended, low-surface-brightness sources made possible by a cryogenic telescope in space; 2.) the use of large format arrays and projected pixel scales that sample the telescope image well provide substantial improvements in angular resolution compared with previous space infrared telescopes; and 3.) its spectrograph has wavelength resolution well-suited to extragalactic studies, as well as high performance arrays that provide a major advance in sensitivity. We show how these capabilities are already leading to new possibilities in studying the structure of nearby galaxies. Combined with recent breakthroughs in high quality imaging at other wavelengths, we can anticipate a substantial improvement in our understanding of how different components of a galaxy relate to each other and how their interactions influence galaxy evolution. In addition, Spitzer is advancing our understanding of the behavior of the polyaromatic hydrocarbon (PAH) emission features, as a function of environment and metallicity. New features are also being discovered due to the high-sensitivity mapping capabilities of the spectrograph. An additional direction for research with Spitzer arises from its deep survey capabilities and the possibility of testing how the spectral energy distributions of galaxies evolve at large look-back times.