Publications (86)83.15 Total impact
-
Article: Tracing interactions in HCGs through the HI
[show abstract] [hide abstract]
ABSTRACT: We present a global study of HI spectral line mapping for 16 Hickson Compact Groups (HCGs) combining new and unpublished VLA data, plus the analysis of the HI content of individual galaxies. Sixty percent of the groups show morphological and kinematical signs of perturbations (from multiple tidal features to concentration of the HI in a single enveloping cloud) and sixty five of the resolved galaxies are found to be HI deficient with respect to a sample of isolated galaxies. In total, 77% of the groups suffer interactions among all its members which provides strong evidence of their reality. We find that dynamical evolution does not always produce HI deficiency, but when this deficiency is observed, it appears to correlate with a high group velocity dispersion and in some cases with the presence of a first-ranked elliptical. The X-ray data available for our sample are not sensitive enough for a comparison with the HI mass; however this study does suggest a correlation between HI deficiency and hot gas since velocity dispersions are known from the literature to correlate with X-ray luminosity.10/1999; -
Article: Sensitive Radio Observations Of High Redshift Dusty Qsos
[show abstract] [hide abstract]
ABSTRACT: We present sensitive radio continuum imaging at 1.4 GHz and 4.9 GHz of seven high redshift QSOs selected for having a 240 GHz continuum detection, which is thought to be thermal dust emission. We detect radio continuum emission from four of the sources: BRI 0952Gamma0115, BR 1202Gamma0725, LBQS 1230+1627B, and BRI 1335Gamma0417. The radio source in BR 1202Gamma0725 is resolved into two components, coincident with the double mm and CO sources. We compare the results at 1.4 GHz and 240 GHz to empirical and semi-analytic spectral models based on star forming galaxies at low redshift. The radio-to-submm spectral energy distribution for BR 1202Gamma0725, LBQS 1230+1627B, and BRI 1335Gamma0417 are consistent with that expected for a massive starburst galaxy, with implied massive star formation rates of order 10 3 M fi year Gamma1 (without correcting for possible amplification by gravitational lensing). The radio-to-submm spectral energy distribution for BRI 0952Gamma0115...09/1999; -
Article: Studying High Redshift Star Forming Galaxies at Centimeter and Millimeter Wavelengths
[show abstract] [hide abstract]
ABSTRACT: t recent results from the Very Large Array (VLA), and from the new 230 GHz MPIfR bolometer array at the IRAM 30m telescope. A wide field survey with the bolometer array indicates a cut-off in the source distribution function at FIR luminosities ? 3 Theta 10 12 L fi . Lastly, we summarize the scientific promise of the New VLA. To appear in Scientific Imperatives at centimeter and meter Wavelengths, ed. M.P van Haarlem and J.M. van der Hulst, (Dwingeloo: NFRA). 1 Introduction The sharp rise of observed flux density, S , with increasing frequency, , in the Rayleigh-Jeans portion of the grey-body spectrum for thermal dust emission from star forming galaxies (S / 3:25 ), leads to a dramatic negative K-correction for observed flux density with increasing redshift. Su09/1999; -
Article: Studying High Redshift Star Forming Galaxies at Centimeter and Millimeter Wavelengths
[show abstract] [hide abstract]
ABSTRACT: We discuss various aspects of centimeter and millimeter wavelength continuum and line observations of high redshift star forming galaxies. Perhaps the most important lesson is that sensitive observations at submm through cm wavelengths reveal a population of active star forming galaxies at high redshift which are unseen in deep optical surveys due to dust obscuration. Current models suggest that this population represents the formation of the spheroidal components of galaxies at z between 2 and 5, constituting about half of the total amount of cosmic star formation from the big bang to the present. High resolution imaging at cm wavelengths provides sub-arcsecond astrometry, and can be used to search for gravitational lensing and/or for the presence of an AGN. Radio continuum observations provide unique information on the magnetic fields in early galaxies, and give a gross indication of the star formation rate, while the radio-to-submm spectral index provides a rough indication of source redshift. Low J transitions of CO are redshifted into the cm bands for z > 2, allowing for sensitive searches for CO emission over large volumes at high redshift. We present recent results from the Very Large Array (VLA), and from the new 230 GHz MPIfR bolometer array at the IRAM 30m telescope. A wide field survey with the bolometer array indicates a cut-off in the source distribution function at FIR luminosities > 3e12 L_sun. Lastly, we summarize the scientific promise of the New VLA. Comment: nfraconf.sty format, 12 pages, revised table. To appear in {\sl Scientific Imperatives at centimeter and meter Wavelengths}, ed. M.P van Haarlem and J.M. van der Hulst, 1999 (Dwingeloo: NFRA)07/1999; -
Article: Submillimeter Imaging Of The Luminous Infrared Galaxy Pair Vv 114
[show abstract] [hide abstract]
ABSTRACT: We report on 450- and 850-m observations of the interacting galaxy pair, VV 114E+W (IC 1623), taken with the SCUBA camera on the James Clerk Maxwell Telescope, and near-infrared observations taken with UFTI on the UK Infrared Telescope. The system VV 114 is in an early stage of a gas-- rich merger. We detect submillimeter (sub-mm) emission extended over 30 00 (12 kpc) and find a good correlation between the spatial distribution of the sub-mm and CO emission. Both the CO and sub-mm emission peak near the reddest region of VV 114E and extend toward VV114W. The bulk of the sub-mm emission resides in the central region showing the largest CO velocity gradients, which is thought to mark the kinematic centroid of the merger remnant. We derived a total dust mass of 1:2 Theta 10 8 M fi , assuming a power-law distribution of dust temperatures. The sub-mm observations suggest that the majority of the dust is relatively cool (T d 20--25 K), and the total dust mass is about 4 times ...04/1999; -
Article: Molecular Gas in the z=2.565 Submillimeter Galaxy SMM J14011+0252
[show abstract] [hide abstract]
ABSTRACT: We report the detection of CO(3-2) emission from the submillimeter-selected luminous galaxy SMM J14011+0252. The optical counterpart of the submillimeter source has been identified as a merger system with spectral characteristics consistent with a starburst at z=2.565. The CO emission confirms the optical identification of the submillimeter source and implies a molecular gas mass of 5x10^{10}h_{75}^{-2} M(sun), after correcting for a lensing amplification factor of 2.75. The large molecular gas mass and the radio emission are consistent with the starburst interpretation of the source. These results are similar to those found for SMM J02399-0136, which was the first submillimeter selected CO source found at high redshift. The CO detections of these two high-redshift submillimeter galaxies suggest the presence of massive reservoirs of molecular gas which is consistent with the inferred high rates of star-formation (1000 M(sun)/yr). These two systems appear to be associated with merger events which may evolve into present day luminous elliptical galaxies. Comment: Accepted by ApJ Letters on Jan. 21, 1999. 7 pages including 3 figures01/1999; -
Article: Effects of Interaction Induced Activities in Hickson Compact Groups: CO and FIR Study
[show abstract] [hide abstract]
ABSTRACT: A study of 2.6 mm CO J = 1 ! 0 and far-infrared (FIR) emission in a distance limited (z ! 0:03) complete sample of Hickson Compact Group (HCG) galaxies was conducted in order to examine the effects of their unique environment on the interstellar medium of component galaxies and to search for a possible enhancement of star formation and nuclear activity. Ubiquitous tidal interactions in these dense groups would predict enhanced activities among the HCG galaxies compared to isolated galaxies. Instead their CO and FIR properties (thus "star formation efficiency") are surprisingly similar to isolated spirals. The CO data for 80 HCG galaxies presented here (including 10 obtained from the literature) indicate that the spirals globally show the same H 2 content as the isolated comparison sample, although 20% are deficient in CO emission. Because of their large optical luminosity, low metallicity is not likely the main cause for the low CO luminosity. The CO deficiency appears linked with the ...12/1997; -
Article: Non-linear Dependence of
[show abstract] [hide abstract]
ABSTRACT: Through the study of a carefully selected sample of isolated spiral galaxies, we have established that two important global physical quantities for tracing star forming activities, L F IR and MH 2 , have non-linear dependence on another commonly cited global quantity LB . Furthermore we show that simple power law relations can effectively describe these non-linear relations for spiral galaxies spanning four orders of magnitude in FIR and MH 2 and nearly three orders of magnitude in LB . While the existence of non-linear dependence of MH 2 (assuming a constant CO-to-H 2 conversion) and L F IR on optical luminosity (LB ) has been previously noted in the literature, an improper normalization of simple scaling by LB has been commonly used in many previous studies to claim enhanced molecular gas content and induced activities among tidally interacting and other types of galaxies. We remove these non-linear effects using the template relations derived from the isolated galaxy sam...07/1997; -
Article: Non-linear Dependence of L(B) on L(FIR) and M(H2) among Spiral Galaxies and Effects of Tidal Interaction
[show abstract] [hide abstract]
ABSTRACT: Through the study of a carefully selected sample of isolated spiral galaxies, we have established that two important global physical quantities for tracing star forming activities, L(FIR) and M(H2), have non-linear dependence on another commonly cited global quantity L(B). Furthermore we show that simple power law relations can effectively describe these non-linear relations for spiral galaxies spanning four orders of magnitude in FIR and M(H2) and nearly three orders of magnitude in L(B). While the existence of non-linear dependence of M(H2) (assuming a constant CO-to-H2 conversion) and L(FIR) on optical luminosity L(B) has been previously noted in the literature, an improper normalization of simple scaling by L(B) has been commonly used in many previous studies to claim enhanced molecular gas content and induced activities among tidally interacting and other types of galaxies. We remove these non-linear effects using the template relations derived from the isolated galaxy sample and conclude that strongly interacting galaxies do not have enhanced molecular gas content, contrary to previous claims. With these non-linear relations among L(B), L(FIR) and M(H2) properly taken into account, we confirm again that the FIR emission and the star formation efficiency L(FIR)/M(H2) are indeed enhanced by tidal interactions. Virgo galaxies show the same level of M(H2) and L(FIR) as isolated galaxies. We do not find any evidence for enhanced star forming activity among barred galaxies. Comment: 19 pages and 5 figures, requires AAS style files, ApJ, accepted06/1997; -
Article: Molecular Gas and Infrared Emission in HCG 31 HCG 92 (Stephan's Quintet) and Tidal Interactions in Compact Group Environment
[show abstract] [hide abstract]
ABSTRACT: We present the interferometric measurements of 2.6 mm CO (J = 1 ! 0) emission (` FWHM 5 00 ) and the analysis of IRAS HIRES images of two Hickson Compact Groups HCG 31 and HCG 92 ("Stephan's Quintet"). The far infrared (FIR) emission is concentrated to a single region in HCG 31 while it is clearly extended and peaks near the group center in HCG 92. CO emission is weak in HCG 31, and the brightest peak occurs in the overlap region between the galaxies A & C. CO emission is detected only in galaxy C (NGC 7319) in HCG 92, and the distribution is highly asymmetric. No CO emission is detected in the interacting pair HCG 92 B & D (NGC 7318 A&B). Gas stripping and star formation by continuous tidal disruptions in compact group environment are discussed as possible explanations for the observed CO deficiency and peculiar molecular gas distribution in HCG 31 and HCG 92. Subject headings: galaxies: clusters: individual (HCG 31, HCG 92) --- galaxies: interactions --- galaxies: evol...12/1996; -
Article: A high-resolution image of atomic hydrogen in the M81 group of galaxies.
[show abstract] [hide abstract]
ABSTRACT: It has long been recognized that interactions between galaxies are important in determining their evolution. The distribution of gas--out of which new stars are formed--is strongly affected; in particular, gas may be concentrated near the nucleus, leading to a burst of star formation. Here we present a map of atomic hydrogen (H I) in the nearest interacting group of galaxies (that dominated by M81), obtained by combining 12 separate fields observed with the Very Large Array. The H I that surrounds M81, M82 and NGC3077 (the most prominent galaxies in the group) is dominated by filamentary structures, clearly demonstrating the violent disruption of this system by tidal interactions. These observations should have detected all H I complexes more massive than 10(6) solar masses, meaning that our map contains all structures that might evolve into new dwarf galaxies.Nature 01/1995; 372(6506):530-2. · 36.28 Impact Factor -
Article: CO Emission in the Radio-loud Quasar 3C 48
[show abstract] [hide abstract]
ABSTRACT: We have used the Owens Valley Millimeter Array to conduct a sensitive search for CO (1 - 0) emission in the radio-loud quasar 3C 48. An emission feature is detected (4σ) at the redshift of the narrow optical emission lines (z = 0.3695). The width of this feature is ~250 km s^-1^(FWHM) similar to that expected for a galactic disk, and the integrated CO line flux implies an H_2_ mass of 7 x 10^10^ M_sun_ (assuming the same CO to H_2_ conversion factor found for giant molecular clouds in the Milky Way). This H_2_ mass is ~30 times that for the Galaxy, and about twice that estimated for ultraluminous IRAS galaxies such as Arp 220 and the UV-excess quasar Mrk 1014. These data support previous suggestions that 3C 48 may have formed from the recent merger of gas-rich galaxies and that the extended nebulosity surrounding the quasar is largely due to a population of young stars which could have been formed from the gas detected here.The Astrophysical Journal 09/1993; 415:L75. · 6.02 Impact Factor -
Article: Near-Infrared, Optical, and CO Observations of the Interacting Galaxy System VV114
[show abstract] [hide abstract]
ABSTRACT: VV114 is a nearby example of a far-infrared bright, high luminosity (LFIR>10(11) L_sun) interacting galaxy pair. At a redshift of z=0.02 it provides an opportunity to study such interacting galaxies at a favorable spatial scale (360 pc/''). This paper presents new high resolution near-infrared (1.25 microns - 3.7 microns) and visible images, visible spectra, and CO (J=1-0) maps of VV114. A picture emerges of a system with widespread massive star formation, throughout both interacting galaxies. The brighter visible galaxy (VV114W) shows HII region-like emission in both visual spectra and near-infrared colors, with no more than two magnitudes of visual extinction. The brightest peak of infrared and radio emission (VV114E) has extreme near-infrared colors and is located at a minimum of visible emission. This indicates a large concentration of dust in the nucleus of VV114E that is nearly entirely obscuring the major luminosity source in this system. This work is supported in part by the NSF and the Eastman Kodak Company. Observations were made at Palomar Observatory with the 5m Hale telescope and at the Owens Valley Radio Observatory.04/1993; 25:801. -
Article: A new observational and numerical study of tidal interactions in M81-M82-NGC3077 system
[show abstract] [hide abstract]
ABSTRACT: A nearby system of interacting galaxies M81-M82-NGC3077 triplet (D = 3.3 Mpc; Freeman & Madore 1988) has been studied using multi-wavelength observations and numerical simulations to obtain a comprehensive understanding on the dynamics and the consequences of tidal interactions in a group environment. The VLA 12-field Mosaic H I observations of 2 x 1.5 deg. region have revealed a vast array of H I filaments which suggests that the severity and extent of tidal disruptions far exceed the previous estimates. A tidal remnant of the former H I disk of M82 extending up to 30 kpc (in projection) is identified for the first time, and the pervasive effects of the tidal disruption are traced into the inner disk by optical and CO observations, including a kinematic trace of a large scale bar potential (Yun, Ho, & Lo 1992). The H I disk of M81 is traced out to 40 kpc in radius, and a large scale (l approx. 20 kpc) velocity anomaly ('High Velocity Trough'), which may be a remnant of a gaseous collision, is found within the disk of M81. The large H I bridge between M81 and NGC 3077 (van der Hulst 1979) is also found to extend approx. greater than 50 kpc further, bending around NGC 3077, toward M82. The total H I detected in this experiment, 5.6 x 10(exp 9) solar mass, represents the majority of the single-dish flux (Appleton, Davies, & Stephenson 1981) and suggests that the bulk of H I found in the region belongs to the three galaxies and the tidal filaments. The impact and details of the tidal interactions have been further examined through the use of numerical techniques. The 'restricted 3-body' approach was used to simulate the observed distribution of tidal H I streamers connecting the three galaxies, and the success of the simulation is further strengthened by the accurate predictions on the gas kinematics.02/1993; -
Article: Aperture Synthesis Observations of M82 in HI
08/1988; 20:1001. -
Article: Disrupted HI Environment Around M82
16:35. -
Article: New 24 Field VLA Mosaic Imaging of HI in the M81 Group
[show abstract] [hide abstract]
ABSTRACT: A previous 12 field mosaic of 21cm HI emission in M81 group has revealed an extensive array of tidal filaments connecting all three core group members M81, M82, and NGC 3077 (Yun et al. 1994). A tidal interaction scenario involving all three galaxies can account for most of the filamentary HI features imaged and has been supported by a numerical calculation (Yun 1997). There are evidence for the HI features extending well beyond the area imaged thus far, particularly towards a fourth member of the group to the southwest, NGC 2976 (Appleton & van der Hulst 1988). Also, additional HI data to the northwest of M82 and southeast of NGC 3077 would help scrutinizing the details of the tidal interaction scenario proposed by our numerical study. Therefore 12 additional fields were observed with the VLA and combined with the existing data to construct a more complete tidal interaction history in M81 group. On the technical side, several different mosaic imaging softwares are tested and compared during the course of image construction.217:374. -
Article: HI and H2 in Luminous Interacting Galaxies (Invited paper)
-1:191. -
Article: What Does HI Tell Us About Hickson Compact Groups?
[show abstract] [hide abstract]
ABSTRACT: The origin of the global HI deficiency in HCGs, previously reported in the literature (Williams & Rood 1987; Huchtmeier 1997), is not yet understood. We consider a large set of parameters that might account for this HI anemia.240:193. -
Article: Ripples and tails in the compact group of galaxies Hickson 54
[show abstract] [hide abstract]
ABSTRACT: HCG 54 has been classified as a compact galaxy group by Hickson, but its nature is uncertain because of its unusual properties. We present here a study of HCG 54 based on deep optical images and spectroscopy as well as high spatial and spectral resolution HI observations obtained at the VLA. Both optical and radio data indicate clearly that HCG 54 is a product of a recent merger involving at least two galaxies. Our optical images have revealed a blue elongated structure associated with HCG 54a embedded in a rounder and redder stellar envelope. Several ripples or shells whose center is located near HCG 54a and b are also detected. These observed features are similar to those found in the numerical simulations of tidal interactions involving two equal mass disk galaxies. This system is embedded in an HI cloud 12 kpc in diameter, and a 20 kpc HI tidal tail emerges from its western edge. Both the HI distribution and kinematics are consistent with a recent history of a deeply penetrating interaction or a merger. Based on the analysis of our new data we propose that HCG 54 is the remnant of a merger in an advanced stage, whose main body is what has been called HCG 54a, while HCG 54b marks the location of a strong starburst induced by the interaction, as evidenced by the Wolf Rayet stellar population that we detect. Optical spectra of HCG 54c and d show HII region features and are interpreted as tidal debris of the collision undergoing active star formation.Astronomy & Astrophysics, v.396, 815-832 (2002).
Top co-authors
Top Journals
Institutions
-
2002–2012
-
University of Massachusetts Amherst
- Department of Astronomy
Amherst Center, MA, USA
-
-
2008
-
National Radio Astronomy Observatory
Charlottesville, VA, USA -
National Autonomous University of Mexico
Mexico City, The Federal District, Mexico
-
-
1995
-
Harvard-Smithsonian Center for Astrophysics
Cambridge, MA, USA
-
